This invention relates to a method of, and apparatus for, detecting faults in the operation of spinning units in open-end spinning machines.
Open-end spinning machines are widely used in the textile industry. The spinning units of such machines are directly fed by a sliver. At the input end of the unit, there is an opener which breaks up the sliver into individual fibres which subsequently pass into a turbine rotating at high speed where they are placed one on top of the other in a groove under the effect of centrifugal force.
This assemblage of fibres is run-off at the center of rotation of the turbine, a heavy twist being imparted to it. The finished yarn is obtained in this way. It travels through a pair of rollers consisting of a driven roller and of a contact pressure roller. The speed of rotation of these rollers determines the take-off speed of the yarn. The yarn is then wound into packages, or yarn cheeses.
The actual spinning unit is in the form of a compact, encased unit between the point at which the sliver enters and the point at which the yarn leaves the turbine. These spinning units are normally in operation day and night. Under normal working conditions, only a few personnel are required for monitoring purposes, for example one person for every 1000 spinning units.
Nevertheless, disturbances which cannot readily be detected from outside can affect individual spindles over a period of time. For example, fibres and dirt can accumulate in the opener section. After reaching a certain size, these accumulations of fibres and dirt drop off and, hence, give rise to whole chains of faults in the yarn. Depending upon their size and nature, these yarn faults can give rise to distrubances either individually or when they appear repeatedly at short intervals, i.e. in chains in the yarn. Another type of fault is produced when fibres or dirt accumulate on the periphery of the turbine. This disturbs the uniform deposition of the individual fibres and produces more or less periodic, abnormally large fluctuations in the thickness of the yarn. There are also other factors which can cause faults in yarn.
However, one feature common to all these faults is that they are more troublesome, the greater the frequency with which they occur and/or the larger they are in size.
The defective operation of any one individual spinning unit is not necessarily attributable to a fault in that unit as it can also be caused by the material delivered to the unit. In many cases, the fault can be eliminated simply by cleaning the unit. In other cases, accumulations of dirt are automatically ejected after a certain time, leaving the unit to function correctly again.
Another feature of open-end spinning machines is that the yarn is wound directly into cheeses. The yarns are further processed in this form. Accordingly, the yarn is not subjected to any rewinding process to allow quality inspection and/or cleaning of the yarn.
If, during production, a spinning unit produces defective yarn over a prolonged period without this being noticed, heavy additional costs can be incurred during weaving or knitting due to the irregular appearance of the woven or knitted article, even in cases where only one among hundreds of cheeses has a fault of this kind.
It is therefore essential to take measures to prevent individual spinning units from producing defective yarn, even temporarily, during the production process. When a fault of this kind occurs, an alarm signal should be given and/or the spinning unit switched off.